In the conventional water treatment process, the water to be treated is exposed to the ozone generated by a mercury UV lamp. Another method is to expose an air stream to UV light irradiation causing the oxygen in the air to generate ozone. This ozonated air is then dissolved into the water to be treated for disinfection to purify water.
There are mainly two methods to generate ozone; one method is a high pressure electric discharge and another is irradiation by a mercury UV lamp. Generally, in the method of UV irradiation by a UV lamp, the UV light generated by the lamp contains two wavelengths: 254 nm (nanometer) and 185 nm. Wavelength of about 185 nm is the main wave band to generate ozone for disinfecting water. Once the UV light having a wavelength of about 254 nm contacts a microorganism, the UV light can be absorbed easily by protein, DNA and RNA in the microorganism. After the absorption of UV light by some protein substances reaches certain strength (dose), the cell membrane will be ruptured, causing the cell to die. In addition, even if the UV dose is not high enough to cause immediate death of the cell, a lower dose of irradiation is sufficient to cause the microorganism to lose its breeding ability which makes people sick.
Ozone is basically a very strong oxidizing agent. As indicated above, when the ozone gets in contact with a microorganism, the disinfecting mechanism includes: 1. Direct destruction of the cell wall causing the cell to die due to the outflow of cell composition; 2. Generation of a by-product of free radical due to the decomposition of ozone causing the cell to die; 3. Destruction of the constitutive structure of the nucleic acid; 4. Interruption of the bonding causing the separation of polymer.
Both UV light and ozone have the ability to perform disinfection, however, in terms of application, especially on disinfecting the drinking water, each has its own merits and shortcomings. The configuration of the equipment is also a basis for determining the quality of the actual effect. To enhance the disinfection effect, a so-called dual mode method by using both of ozone and UV light methods can be employed in the disinfection apparatus. In this dual mode method, ozone generated from the UV light irradiation having a short wavelength of around 185 nm is mixed to dissolve in the water to be disinfected. And, UV light having a wavelength of around 254 nm generated by a UV mercury lamp is employed to irradiate water directly.
In the disinfection process design, the ozone generated by a UV lamp is continuously extracted and dissolved into the water for purification, and thereby carrying out the first step of disinfection. The ozonated water is then guided to the exterior of the UV lamp that generated the original ozone. The UV light having a wavelength of 254 nm is then used to irradiate the ozonated water that further enhances the disinfection effect. In the mean time, part of the ozone is reduced which not only makes the water finally flowing out of the apparatus thoroughly be disinfected but also make the excessive and residual ozone be eliminated to prevent human health from being impaired.
In the prior art, the relevant patents have resolved the system design problems such as the generation of ozone and its injection into the water, as well as combining the disinfection of UV radiation. However, they fail to demonstrate their performance of effectively prolonging the irradiation time of UV light and the functioning time of ozone, as well as enhancing the basic requirement of disinfection by mixing and dissolving the ozone in the water homogeneously.
The disinfecting effect of ultraviolet-and-ozone essentially depends on the amount of dosage and the duration of contact time. The UV disinfection usually considers what is known as an UV dose problem. An UV dose refers to an UV fluence rate multiplied by its irradiation time. To achieve a certain disinfection capability, the UV light must have sufficient disinfection strength and a long enough irradiation response time. In general, the irradiation strength of any commercially available UV lamps can all meet the requirement in the initial stage of usage by irradiating the water through a quartz tube to achieve the disinfection effect. The effective reaction time depends on the length of the reaction chamber disregarding whether the UV lamp operates for 24 hours a day or is controlled by means of an on/off switch. A typical commercial product has a contact length of about 30 cm.
Although the description of some prior arts indicates the employment of the natural spiral effect by making use of the impact of water back-flow to extend the irradiation time, the effect of that extension is just within 1.5 times, which is equivalent to around 40 cm of contact length.
Similar to the UV-light disinfection, the evaluation of the disinfection effect of ozone employs the so-called CT value that is a product of the concentration C and the contact time T. Consequently, in order to produce an effective disinfection, sufficient contacting time is necessary to have the ozone mix with and dissolve in the water.
In terms of water treatment, relevant patents as illustrated in FIG. 1 are U.S. Pat. No. 5,266,215 of Engelhard's (Water purification unit) and U.S. Pat. No. 5,540,848 of Engelhard's (Filter retainer for water purification unit). In both cases, the water to be treated is created a vortex pattern 402 surrounding the UV radiation source 401 to eliminate bacteria in the water and microorganisms that are harmful to human health.
Again as shown in FIG. 2 U.S. Pat. No. 6,245,229B1, Kool et al.'s (point-of-use water treatment system) also uses water to be treated to create a vortex pattern 412 surrounding the UV radiation source (not shown in diagram) to eliminate bacteria in water and also microorganisms that are harmful to human health. However, these patents are all simple designs of a spiral water column, and the exposure time to UV radiation is very limited.
Again, as shown in FIG. 3 of U.S. Pat. No. 4,273,660, Beitzel's (purification of water through the use of ozone and ultraviolet light) traditionally soaks the water to be treated 432 directly around the UV lamp tube 431. This patent does not have any spiral design of water flow, so the disinfection effect is also very limited.
In addition, as shown in FIG. 4 of U.S. Pat. Ser. No. 5,707,594, Austin's (Pathogen control system) uses a spiral Teflon (polytetrafluoroethylene) transmitting tube 424 that wraps around the UV Lamp 421 to transmit water. The spiral Teflon tube itself causes the UV irradiation to attenuate, and is therefore unable to achieve the disinfection objective. Furthermore, the Teflon tube is lengthy and expensive, therefore is not economical.
Consequently, how to extend the water flow of water treatment so that the mixture of ozone and water can be well mixed to enhance the disinfection effect, and how to ensure this ozonated water is sufficiently irradiated to enhance the ultraviolet disinfection effect have become the objects of this claim.